DELTA-CONOTOXIN GMVIA, A NOVEL PEPTIDE FROM THE VENOM OF CONUS-GLORIAMARIS

A novel peptide toxin, delta-conotoxin GmVIA, was purified from the ve nom of Conus gloriamaris, a mollusc-hunting snail. It consists of 29 a mino acids, including six Cys residues: [GRAPHICS] The pattern of disu lfide connectivity (4-19, 12-24, and 18-29) is the same as for the ome ga-conotoxins, which are Ca2+ channel ligands. However, the peptide do es not compete with omega-conotoxin for binding to membrane preparatio ns from frog, rat, and chick brain. Instead, initial electrophysiologi cal results suggest that the peptide induces action potential broadeni ng in molluscan neurons by slowing down Na+ current inactivation. Synt hetic delta-conotoxin GmVIA was prepared by solid-phase methods and ap peared identical in all respects to the natural material. The chromato graphic behavior of native and reduced delta-conotoxins is quite remar kable, suggesting that the disulfides form a core which forces hydroph obic residues to point out toward the solvent.